A low-power flame ion detection circuit and method with adjustable sensitivity

Abstract

The present invention discloses a low-power flame ionization detection circuit and method with adjustable sensitivity. The circuit includes a CPU, a switching tube Q1, a transformer T1, a high-voltage circuit, a switching circuit, and an ion current detection circuit. The CPU generates a PWM pulse modulation signal to the switching tube Q1, which is connected to the input end of the transformer T1. The output end of the transformer T1 is connected to a capacitor C1 through a diode D1. One end of the capacitor C1 is connected to the high-voltage circuit and the other end is connected to the switching circuit. Another end of the output end of the transformer T1 is coupled to a resistor network through a capacitor C2. The flame detection excitation signal of the present invention is generated without delay, which reduces flame detection time, lowers power consumption, and extends battery life.

Description

Technical Field

[0001] The present invention relates to the technical field related to cookers, and in particular to a low-power flame ion detection circuit with adjustable sensitivity and a method thereof. Background Art

[0002] Gas stoves use flame ionization detection for flameout protection, but most stoves are battery-powered. Existing flame ionization circuits use a transformer to boost the voltage, providing both the ignition medium voltage and the flame detection excitation signal generation circuit. The detection excitation signal voltage is relatively high, while the battery voltage is the same as two dry-cell batteries. This results in high power consumption for the flame detection excitation signal, typically tens of milliamps. While intermittent detection reduces the average combustion current, it still places a heavy strain on the battery. Furthermore, because the excitation signal is battery-powered, the battery voltage decreases over time, leading to a decrease in the excitation signal amplitude, thus reducing the sensitivity of the flame detection. This can lead to false detections at low battery voltages, making flameout more likely. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a low-power flame ion detection circuit and method with adjustable sensitivity.

[0004] A low-power flame ionization detection circuit with adjustable sensitivity includes a CPU, a switch tube Q1, a transformer T1, a high-voltage circuit, a switch circuit, and an ion current detection circuit. The CPU generates a PWM pulse modulation signal to the switch tube Q1, and the switch tube Q1 is connected to the input end of the transformer T1. The output end of the transformer T1 is connected to a capacitor C1 through a diode D1. One end of the capacitor C1 is connected to the high-voltage circuit and the other end is connected to the switch circuit. The output end of the transformer T1 is coupled to a resistor network through a capacitor C2.

[0005] As a preferred embodiment, the CPU, switch tube Q1, transformer T1, diode D1, capacitor C1, switch circuit and high-voltage circuit constitute a high-voltage ignition circuit. The high-voltage circuit includes a transformer T2 and a switch tube U2. The input end of the transformer T2 is connected to the switch tube U2, and the output end is connected to the ignition electrode; the capacitor C1 boosts the voltage, the switch tube U2 is turned on, the capacitor C1 is connected to the input end of the transformer T2, and the output end of the transformer T2 generates high voltage.

[0006] As a preferred embodiment, the switching circuit includes a switch tube U1 and a diode D2. The transformer T1 boosts the voltage, and a flyback switch boost is generated at the output end of the transformer T2. The switch tube U1 is turned on, and the diode D2 charges the capacitor C1 after rectification.

[0007] As a preferred embodiment, a capacitor C3 is further included, one end of the capacitor C3 is connected to the common end, and the other end is connected to the resistor network.

[0008] As a preferred embodiment, the ion current detection circuit includes a capacitor C2, a capacitor C3, a resistor network and a CPU.

[0009] As a preferred embodiment, the resistor network includes resistors R1, R2 and R3, and R3 is connected to the flame electrode.

[0010] A low-power flame ionization circuit detection method with adjustable sensitivity is applied to the ignition and combustion stages of an igniter, and includes the following steps:

[0011] Start the PWM unit regularly and control the on and off of the switch tube U1 at the same time;

[0012] Determine whether there is flame;

[0013] If no flame is generated, it enters the protection state.

[0014] As a preferred embodiment, when the detection method is applied to the ignition stage, it specifically includes the following steps: Step 1, enabling the PWM unit, starting the timer, and controlling the switch tube U1 to turn on;

[0015] Step 2: The first stage timer stops and determines whether the voltage of capacitor C3 is lower than the threshold. If so, the ignition is successful and the combustion stage begins.

[0016] Step 3: Otherwise, detect the voltage of capacitor C1 and control the switch tube U2 to ignite;

[0017] Step 4: If the second stage timing is up, go to step 5, or return to step 1;

[0018] Step 5: If the ignition fails again, enter the protection state.

[0019] As a preferred embodiment, when the detection method is applied to the combustion stage, it specifically includes the following steps: Step 1, regularly turning on the PWM unit and turning off the switch tube U1;

[0020] Step 2: Determine whether the voltage of capacitor C3 is lower than the threshold. If so, it is determined that flame is generated and the combustion state is maintained; otherwise, it is determined that no flame is generated and the flameout protection is entered;

[0021] Step 3: If the combustion is normal, enter the low power consumption mode and return to the first step after the timer ends.

[0022] As a preferred embodiment, when the battery voltage decreases, the pulse width of the PWM is adjusted to a constant excitation signal voltage amplitude.

[0023] Based on the above-mentioned low-power flame ionization detection circuit and method with adjustable sensitivity, the CPU generates a PWM pulse modulation signal to the control terminal of the switch tube Q1, generating a switching signal at the primary of transformer T1, which boosts the voltage. This generates a flyback switch boost at the output of transformer T2, and the rectifier diode D2 charges capacitor C1. When capacitor C1 reaches a predetermined voltage, U2 turns on, capacitor C1 discharges to the primary of transformer T2, and the secondary of transformer T2 generates a high voltage, which discharges through the ignition electrode, thereby igniting the gas. The present invention determines whether a flame state exists by determining the ion current, thereby generating flameout protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a circuit for flame ionization detection according to an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of the ignition process of an embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the combustion process of an embodiment of the present invention; DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0028] When the flame detection motor contacts the flame, a weak flame ion current is generated that flows through the burner's ground circuit. This signal is amplified and then switched through the relay output contacts to control external devices. The ion current determines whether the flame state exists, thereby providing flameout protection. In this embodiment, the CPU, switch Q1, transformer T1, diode D1, capacitor C1, switch U1, capacitor C2, capacitor C3, resistor R1, resistor R2, and resistor R3 form an ion current detection circuit that generates a flame detection excitation signal. Compared to conventional circuits, the circuit in this embodiment can generate a flame detection excitation signal without delay, reducing flame detection time, power consumption, and extending battery life.

[0029] A low-power flame ionization detection circuit with adjustable sensitivity, reference Figure 1 , including a CPU, a switch tube Q1, a transformer T1, a high-voltage circuit, a switch circuit and an ion current detection circuit. The CPU generates a PWM pulse modulation signal to the switch tube Q1, and the switch tube Q1 is connected to the input end of the transformer T1. The output end of the transformer T1 is connected to the capacitor C1 through the diode D1. One end of the capacitor C1 is connected to the high-voltage circuit and the other end is connected to the switch circuit; the output end of the transformer T1 is coupled to the resistor network through the capacitor C2; the ion current detection circuit includes capacitor C2, capacitor C3, the resistor network and the CPU.

[0030] In the first embodiment, referring to Figures 1 to 3 The switch tube Q1, transformer T1, and rectifier diode D1 form a flyback switch boost circuit. When the switch tube Q1 is turned on, power flows through the primary of the transformer T1 to excite the transformer T1. When the switch tube Q1 is turned off, the transformer T1 generates a back electromotive force, which charges the energy storage C1 through the rectifier diode D1. The switch tube Q1 can be a triode switch tube or a MOS switch tube. In this embodiment, a MOS tube is preferably used.

[0031] When C1 approaches 100V, the voltage of capacitor C3 is detected to determine whether ignition has occurred. If ignition has not occurred, capacitor C1 continues to charge. When capacitor C1 reaches 150V, it is determined whether the ignition voltage has been reached. The ignition voltage is detected through the secondary tap. When the ignition voltage is reached, the PWM pulse modulation signal output is stopped, and the switch tube U2 is controlled to conduct. At this time, switch tube U1 automatically shuts off due to the lack of current, diode D2 conducts, and C1 discharges through the primary of high-voltage transformer T2, generating an air spark discharge at the ignition electrode to ignite the gas. Among them, switch tubes U1 and U2 are preferably thyristor switches.

[0032] In the second embodiment, referring to Figures 1 to 3 ,After ignition, the timer sets the timing time and regularly turns on the PWM unit. The PWM unit sets the pulse width according to the battery voltage to maintain the constant excitation voltage. The PWM excitation pulse width at this time is smaller than the pulse width during ignition;

[0033] Turn off switches U1 and U2, prohibiting the charging of capacitor C1. Charging the energy storage capacitor C1 will cause the excitation signal to rise slowly during the charging process, and energy is stored in capacitor C1. Capacitor C1 leaks during the non-detection period, increasing power consumption. Turning off switch U1 will cause the excitation signal to reach the preset value immediately.

[0034] When the battery voltage decreases, the PWM pulse width can be adjusted to keep the excitation signal voltage amplitude constant, thereby ensuring the flame detection sensitivity at low battery voltage.

[0035] refer to Figure 1 The CPU, switch tube Q1, transformer T1, diode D1, capacitor C1, switching circuit and high-voltage circuit constitute a high-voltage ignition circuit. The high-voltage circuit includes a transformer T2 and a switch tube U2. The input end of the transformer T2 is connected to the switch tube U2, and the output end is connected to the ignition electrode. The capacitor C1 boosts the voltage, the switch tube U2 is turned on, the capacitor C1 is connected to the input end of the transformer T2, and the output end of the transformer T2 generates high voltage. The switching circuit includes a switch tube U1 and a diode D2. The transformer T1 boosts the voltage, generating a flyback switch boost at the output end of the transformer T2. The switch tube U1 is turned on, and the diode D2 rectifies and charges the capacitor C1.

[0036] The CPU generates a PWM pulse modulation signal to switch Q1, generating a switching signal at the primary of transformer T1. Transformer T1 then boosts the voltage, generating a flyback switch boost at the output of transformer T2. This voltage is rectified by diode D2 and charges C1, turning U1 on. When C1 reaches a predetermined voltage, U2 turns on, discharging C1 into the primary of T2. This generates a high voltage exceeding 10,000 volts at the secondary of transformer T2, which discharges through the ignition electrode, igniting the gas.

[0037] The device also includes a capacitor C3, one end of which is connected to the common terminal and the other end to the resistor network. The voltage of capacitor C3 is proportional to the ion current. The greater the ion current, the lower the negative voltage of C3. The higher the amplitude of the excitation signal and the greater the ion current, the more sensitive the sensing circuit.

[0038] The resistor network includes resistors R1, R2, and R3, with R3 connected to the flame electrode. Resistor R3 is connected to the flame detection electrode in three situations: 1. No flame. In this case, the circuit between the detection electrode and ground is open. No current flows through R3, and the voltage on C3 is the charging voltage of R1 and R2. Because positive and negative energy are equal, the voltage on C3 is zero.

[0039] Second, when there is a flame, the unidirectional ion current between the flame electrode and ground acts as a diode. That is, the excitation signal is shunted through R3 during the positive half-cycle, while the negative half-cycle is open circuit or has a low current. This results in a negative voltage across C3 due to the positive and negative charging.

[0040] 3. There is a short circuit or leakage between the flame electrode and the ground. When the short circuit or leakage is large, the shunt is large and the negative voltage on capacitor C3 is small.

[0041] Through the coupling of capacitor C2, charging and discharging currents are generated on resistors R1, R2, R3 and capacitor C3. When flame is generated, negative voltage is generated on capacitor C3. This negative voltage can pass through the bias circuit and serve as the input of the comparator. The output of the comparator is used to determine whether the negative voltage of the amplified capacitor C3 is lower than the threshold, thereby determining whether flame is generated. Alternatively, the voltage of capacitor C3 can be amplified by an amplifier and collected and determined by A / D.

[0042] A low-power flame ionization circuit detection method with adjustable sensitivity, reference Figure 2 and Figure 3 The detection method is applied to the ignition stage and combustion stage of the igniter, and includes the following steps:

[0043] The PWM unit is started at a fixed time and the on / off of the switch tube U1 is controlled at the same time. This circuit controls the on / off of the switch tube U1. When a flame detection excitation signal is generated, the voltage of the transformer T1 has no charging circuit on the energy storage capacitor C1, and the flame excitation signal can reach the preset amplitude without delay.

[0044] Determine whether there is flame generated. The flame at this time includes the flame at ignition and the flame state of burning; if no flame is generated, enter the protection state.

[0045] In one embodiment, when the detection method is applied to the ignition stage, the circuit principle is as described in the first embodiment above, specifically including the following steps: Step 1, enabling the PWM unit, starting the timer, and controlling the switch tube U1 to be turned on; controlling the switch U1 to be turned on, when the flame detection excitation signal is generated, the transformer T1 voltage has no charging circuit on the capacitor C1, and the flame excitation signal can reach the preset amplitude without delay.

[0046] Step 2: The first-stage timer stops timing and determines whether the voltage of capacitor C3 is lower than the threshold. If so, the ignition is successful and enters the combustion stage; the CPU controls PWM generation and detects whether the flame is generated within the time window, that is, the first-stage timing, to avoid interference of ignition spark discharge on flame detection and improve the reliability of ignition detection.

[0047] Step 3: Otherwise, detect the voltage of capacitor C1 and control the switch tube U2 to ignite. At this time, the switch tube U1 is automatically turned off due to no current, the diode D2 is turned on, the capacitor C1 is discharged through the primary of the high-voltage transformer T2, and an air spark discharge is generated at the ignition electrode to ignite the gas.

[0048] Step 4: If the second stage timing is up, go to step 5, or return to step 1; if step 3 fails, go to step 5 to complete the flameout protection, or return to step 1 to re-ignite.

[0049] Step 5: If the ignition fails again, enter the protection state.

[0050] In another embodiment, when the detection method is applied to the combustion stage, the circuit principle is as described in the second embodiment above, with reference to Figure 3 , specifically including the following steps: Step 1, regularly turn on the PWM unit and disconnect the switch tube U1; transformer T1 generates a boost voltage, and the working current is large. The longer the working time, the greater the power consumption. The existence of U1 greatly shortens the signal generation time and reduces power consumption. The switch tube U1 is turned off so that the excitation signal reaches the preset value immediately.

[0051] Step 2: Determine whether the voltage of capacitor C3 is lower than the threshold. If so, flame is detected and the combustion state is maintained. Otherwise, flame is detected and the flameout protection is activated. Detect capacitor C3 and the output of the comparator. The comparator circuit can set a threshold so that the comparator does not flip when there is no flame or leakage, and flips when there is flame. The presence of flame is determined based on the comparator output. When a flame is present, a negative voltage is generated on capacitor C3. This negative voltage can pass through the bias circuit and serve as the input of the comparator. The comparator output can be used to determine whether the negative voltage of C3 is lower than the threshold, thereby determining whether flame is present. Alternatively, the voltage of C3 can be amplified by an amplifier and then collected and determined using A / D.

[0052] Step 3: If the combustion is normal, the system enters low power consumption mode and returns to step 1 after the timing ends. The flame detection excitation signal is generated without delay, which reduces the flame detection time and power consumption.

[0053] When the battery voltage decreases, the PWM pulse width is adjusted to maintain a constant excitation signal voltage amplitude. The PWM pulse width is calculated based on the battery voltage to produce a constant-amplitude excitation signal. By adjusting the PWM pulse width as the battery voltage decreases, the excitation signal voltage amplitude is maintained constant, ensuring flame detection sensitivity at low battery voltages. In this embodiment, the igniter operating current is set to 5-10mA, resulting in a 1.5mA decrease in the average excitation signal current.

[0054] The above is an explanation of a low-power flame ion detection circuit and method with adjustable sensitivity of the present invention, which is used to help understand the present invention. However, the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, and simplifications made without departing from the principles of the present invention should be equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A low-power flame ionization detection circuit with adjustable sensitivity, characterized in that: The system includes a CPU, a switch tube Q1, a transformer T1, a high-voltage circuit, a switch circuit, and an ion current detection circuit. The CPU generates a PWM pulse modulation signal to the switch tube Q1. The switch tube Q1 is connected to the input end of the transformer T1. The output end of the transformer T1 is connected to the capacitor C1 through a diode D1. One end of the capacitor C1 is connected to the high-voltage circuit and the other end is connected to the switch circuit. The output end of the transformer T1 is coupled to the resistor network through a capacitor C2. The CPU, switch tube Q1, transformer T1, diode D1, capacitor C1, switch circuit and high-voltage circuit constitute a high-voltage ignition circuit. The high-voltage circuit includes a transformer T2 and a switch tube U2. The input end of the transformer T2 is connected to the switch tube U2, and the output end is connected to the ignition electrode. The capacitor C1 boosts the voltage, the switch tube U2 is turned on, the capacitor C1 is connected to the input end of the transformer T2, and the output end of the transformer T2 generates high voltage. The switching circuit includes a switch tube U1 and a diode D2. The transformer T1 boosts the voltage, and a flyback switch boost is generated at the output end of the transformer T2. The switch tube U1 is turned on, and the diode D2 rectifies and charges the capacitor C1. The device further includes a capacitor C3 , one end of which is connected to the common terminal, and the other end of which is connected to the resistor network.

2. The low-power flame ionization detection circuit with adjustable sensitivity according to claim 1, characterized in that: The ion current detection circuit includes a capacitor C2, a capacitor C3, a resistor network and a CPU, one end of the capacitor C2 is connected to the output end of the transformer T1, the other end is connected to the first end of the resistor network, the second end of the resistor network is connected to the flame electrode, and the third end of the resistor network is connected to the capacitor C3.

3. The low-power flame ionization detection circuit with adjustable sensitivity according to any one of claims 1 to 2, characterized in that: The resistor network includes resistor R1, resistor R2 and resistor R3, one end of the resistor R3 is connected to the flame electrode, and the other end is connected to the resistor R1 and one end of the resistor R2, the other end of the resistor R1 is connected to the capacitor C2, and the other end of the resistor R2 is connected to the capacitor C3.

4. A detection method for the low-power flame ionization detection circuit with adjustable sensitivity according to any one of claims 1 to 3, wherein the detection method is applied to the ignition stage and the combustion stage of the igniter, and is characterized in that: The following steps are involved: Start the PWM unit regularly and control the on and off of the switch tube U1 at the same time; Determine whether there is flame; If no flame is generated, it enters the protection state; The PWM unit is a PWM control module of the CPU. The PWM unit outputs a PWM pulse signal to the control end of the switch tube Q1 to drive the step-up transformer T1 to work and control the high-voltage ignition circuit to store energy; The CPU controls the switching of the switch U1 to control the charging and discharging of the capacitor C1.

5. The flame ionization circuit detection method with adjustable sensitivity and low power consumption according to claim 4, characterized in that: When the detection method is applied to the ignition stage, it specifically includes the following steps: Step 1, enabling the PWM unit, starting the timer to count, and controlling the switch tube U1 to turn on; Step 2: The first stage timer stops and determines whether the voltage of capacitor C3 is lower than the threshold. If so, the ignition is successful and the combustion stage begins. Step 3: Otherwise, detect the voltage of capacitor C1 and control the switch tube U2 to ignite; Step 4: If the second stage timing is up, go to step 5, or return to step 1; Step 5: If the ignition fails again, enter the protection state.

6. The flame ionization circuit detection method with adjustable sensitivity and low power consumption according to claim 4, characterized in that: When the detection method is applied to the combustion stage, it specifically includes the following steps: Step 1, regularly turning on the PWM unit and disconnecting the switch tube U1; Step 2: Determine whether the voltage of capacitor C3 is lower than the threshold. If so, it is determined that flame is generated and the combustion state is maintained; otherwise, it is determined that no flame is generated and the flameout protection is entered; Step 3: If the combustion is normal, enter the low power consumption mode, and return to step 1 after the timer ends.

7. The flame ionization circuit detection method with adjustable sensitivity and low power consumption according to claim 4, characterized in that: When the battery voltage decreases, the PWM pulse width is adjusted to a constant excitation signal voltage amplitude.

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